fix for styleparser

[danielcherubini]

Styleblock missing had uncaught exception

so if theres no style block, then resolve with empty string.

[codecov]

Codecov Report

Merging #67 into develop will not change coverage.
The diff coverage is 66.66%.

@@           Coverage Diff            @@
##           develop      #67   +/-   ##
========================================
  Coverage    86.54%   86.54%           
========================================
  Files           17       17           
  Lines          431      431           
========================================
  Hits           373      373           
  Misses          58       58

Impacted Files	Coverage Δ
src/parser/style.js	81.81% <66.66%> (ø)	⬆️

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